infoschema, util: add table events_statements_summary_by_digest_history (#13813)

[djshow832]

conflicting files:
config_test.go
const.go
global_vars_cache.go
set.go
statement_summary.go
sysvar.go
tables.go
tables_test.go
tidb_vars.go
varsutil.go

What problem does this PR solve?

Add a history table for statement summary for storing summaries that expired from events_statements_summary_by_digest.

What is changed and how it works?

Add a virtual table events_statements_summary_by_digest_history. When a summary expires from events_statements_summary_by_digest, put it into events_statements_summary_by_digest_history.
There's a system variable tidb_stmt_summary_history_size to control the history size for each summary.

Check List

Tests

• Unit test
• Manual test

Code changes

• Has exported function/method change
• Has interface methods change

Side effects

• Possible performance regression
• Increased code complexity

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release note

• Add a history table events_statements_summary_by_digest_history to store history summaries of events_statements_summary_by_digest.

[djshow832]

/run-all-tests

[bb7133]

LGTM

[crazycs520]

LGTM